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High flow nasal oxygen during sedation in the cardiac catheterisation laboratory

A randomized controlled trial

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  • Authors
  • Aaron Conway

    Peter Munk Cardiac Centre, UHN & Lawrence S. Bloomberg Faculty of Nursing, University of Toronto

  • Navpreet Kamboj

    Lawrence S. Bloomberg Faculty of Nursing, University of Toronto

  • Kristina Chang

    Toronto General Hospital, UHN

  • Matteo Parotto

    Toronto General Hospital, UHN

Protocol

Participants

CONSORT diagram


  • From August 2019 to March 2020, we screened 270 patients undergoing CIED procedures.
  • A total of 130 participants were randomized.
  • One participant was subsequently excluded from the study because their procedure was cancelled after the randomization was performed.
  • One further participant, who was randomized to the HFNO group, had their procedure rescheduled to a time that the Research Assistant was not available. As such, this participant received oxygen via standard face mask and TcCO2 data were not collected.
  • Two participants who were randomized to HFNO did not receive this intervention at all during procedures at the discretion of the Anesthesia Assistant, with the rationale that the high flow of oxygen interfered with capnography monitoring.
  • For two participants, the TcCO2 sensor failed to callibrate prior to commencement of the procedure, so they were not able to be included in the analyses for the TcCO2 outcomes.

Reasons for exclusion from the trial

The total number of exclusions displayed here is not equal to the actual total number of participants not meeting the inclusion criteria (displayed in the CONSORT diagram), as some participants had multiple reasons for exlcusion.

Sample characteristics

Characteristic High Flow nasal oxygen, N = 641 Face mask oxygen, N = 651
Age (years) 67 (14) 70 (13)
Gender
Female 19 (30%) 17 (26%)
Male 45 (70%) 47 (72%)
Prefer not to say 0 (0%) 1 (1.5%)
Other 0 (0%) 0 (0%)
Smoking history
Never 23 (36%) 25 (38%)
Current 7 (11%) 7 (11%)
Past 34 (53%) 33 (51%)
Obstructive sleep apnea 17 (27%) 18 (28%)
Uses CPAP 9 (14%) 12 (18%)
Admission source
Ward 17 (27%) 18 (28%)
Day surgery 45 (70%) 44 (68%)
CVICU 2 (3.1%) 3 (4.6%)
CICU 0 (0%) 0 (0%)
ASA classification status
I 0 (0%) 0 (0%)
II 0 (0%) 0 (0%)
III 21 (33%) 16 (25%)
IV 43 (67%) 49 (75%)
Procedure
PPM 11 (17%) 17 (26%)
PPM generator change 6 (9.4%) 7 (11%)
PPM lead revision 0 (0%) 1 (1.5%)
ICD 19 (30%) 13 (20%)
ICD generator change 10 (16%) 13 (20%)
ICD lead revision 2 (3.1%) 0 (0%)
CRT-D 11 (17%) 11 (17%)
CRT-P 2 (3.1%) 2 (3.1%)
Wound revision 0 (0%) 0 (0%)
Other 3 (4.7%) 1 (1.5%)
Charlson Comorbidity Index 4.46 (2.14) 5.15 (2.51)
Total dose of midazolam (mg) 1.58 (0.84) 1.45 (0.71)
Total dose of propofol (mg) 100 (126) 88 (104)
Total dose of fentanyl (mcg) 71 (28) 76 (56)

1 Statistics presented: mean (SD); n (%)


  • The sample was mostly elder and predominantly male.
  • Anesthesia Assistants’ rated the ASA Physical Classification Status for participants as either III or IV, reflecting the underlying cardiovascular disease and multiple comorbidities.
  • Obstructive sleep apnea was common, with 27% of participants reporting a diagnosis of this condition.
  • About 20% of procedures were for cardiac resnchronisation therapy.

TcCO2

TcCO2 throughout procedures

Dotted lines display the time where 50% and 75% and 90% of procedures were completed

Peak TcCO2 against baseline

The average difference (95% credible intervals) in peak TcCO2 between groups was 0.0mmHg (-1.4, 1.4).

Mean TcCO2 against baseline

The average difference (95% credible intervals) in mean TcCO2 between groups was -0.1mmHg (-1.3, 1.1).

Missing CO2 measurements


  • For two participants, the Sentec VSign 2 sensor failed to calibrate, so these participants were not able to be included in the analyses for the TcCO2 outcomes.
  • For a small number of participants there was a delay in calibration of the Sentec VSign 2 sensor, resulting in a small amount missing data for a period of time at the start of procedures.
  • One participant had their procedure rescheduled to a time that the researchers were unavailable. As such, TcCo2 measured for this participant.

Secondary outcomes

Comfort with the oxygen device

The treatment effect (95% credible intervals) was 0.2 (-0.5, 0.8).

Anesthesia Assistant rating for difficulty using the oxygen device

The treatment effect (95% credible intervals) was -1.1 (-1.9, -0.2).

Anesthesia Assistant rating for difficulty maintaining oxygenation status

The treatment effect (95% credible intervals) was -2.1 (-3.0, -1.1).

Iowa Satisfaction with Anesthesia Scale scores

The treatment effect (95% credible intervals) was 0.0 (-0.3, 0.2).

SpO2 throughout procedures

Missing SpO2 measurements

The Sentec VSign 2 sensor location (forehead) was chosen to optimise the accuracy of TcCo2 measurement, as this was the primary outcome for this study. As such, the SpO2 measurements were unreliable for some participants.

Oxygen device settings

Oxygen flow rate in litres per minute for each participant


  • Participants randomized to the HFNO group received flow rates at 50 litres per minute or higher for the majority of the time.
  • One participant who was randomized to receive HFNO had their procedure rescheduled to a time that the Research Assistant was not available. As such, this participant received oxygen via standard face mask.
  • Two participants who were randomized to HFNO did not receive this intervention at all during procedures at the discretion of the Anesthesia Assistant, with the rationale that the high flow of oxygen interfered with capnography monitoring.
  • Four participants who were randomized to HFNO stopped receiving this intervention at a certain timepoint during procedures at the discretion of the Anesthesia Assistant, with the rationale that the high flow of oxygen interfered with capnography monitoring.

Oxygen flow rate as a proportion of the total time of all procedures


  • Participants randomized to the HFNO group received flow rates at 50 litres per minute or higher for the majority of the time.

Oxygen to air ratio for each participant randomized to high flow nasal oxygen


  • Most participants randomized to HFNO received an oxygen to air ratio of 50% for their entire procedure.
  • The oxygen to air ratio was increased higher than 50% for only a small number of participants, at the discretion of the Anesthesia Assistant to improve oxygenation.
  • For participants who were switched to oxygen supplementation via a standard facemask, the oxygen to air ratio was assumed to be 1.0.

Data

Codebook

The dataset can be downloaded for secondary use. This table displays a summary of the variables collected for this study along with their types, levels (for factors) and the extent of missingness per variable.

Reproducibility